1. Field of the Invention
The present invention relates to pharmaceutical preparations of heparin, biologically active peptides and proteins and antineoplastic drugs suitable for enteral administration.
2. Description of the Prior Art
As a result of recent progress in the field of biochemistry, many biologically active compounds such as heparin, proteins and antineoplastic drugs are now available for clinical use. However, because these compounds possess low lipophilicity and can be destroyed in the gastrointestinal tract by enzymes of cleavage and in the stomach by acid hydrolysis, methods of administering these compounds orally have not kept pace with their synthesis and identification. Typical of this situation is the case of insulin. It has long been established that insulin is an effective endogenous hormone useful in the treatment of diabetes mellitus. Furthermore, the intact insulin molecule is known to pass through the intestinal wall of various animals under specified conditions. However, adult animals (including humans) absorb insulin poorly when it is orally administered. This is probably due to a combination of factors: destruction of intact insulin molecules as previously discussed and slow passage of intact insulin molecules through the intestinal wall because of low lipophilicity. Consequently, therapeutic use of insulin is limited by the necessity of administering it parenterally, particularly by intravenous or intramuscular injection.
The desire to avoid parenteral administration of insulin has stimulated research efforts in other modes of administration, among which oral administration is the most attractive. Although efforts have been made to develop oral hypoglycemic agents other than insulin, a great deal of effort has also been concentrated on the modification of insulin in such a way that an immunologically intact and metabolically competent insulin molecule can be absorbed through the intestine so that insulin itself or a derivative thereof may be orally administered. The search in this area has been concentrated in three directions: the development of adjuvants, the co-administration of enzymatic inhibitors, and the development of liposomes. Adjuvants used with insulin include resorcinols, non-ionic surfactants such as polyoxyethylene oleyl ether, and n-hexadecyl polyethylene ether. Enzyme inhibitors include pancreatic trypsin inhibitor, diisopropylfluorophosphate (DFP), and trasylol. Liposomes include water-in-oil-in-water insulin emulsions as well as conventional liposomes.
The co-administration of enzyme inhibitors has had some degree of success, particularly when used with duodenal administration. Adjuvants such as hexylresorcinol have been administered with insulin to diabetic patients to give systemic, hypoglycemic effects. However, some adjuvants are limited to successful intra-jejunal administration. Compared to the other types of oral insulin preparations, liposomes have been relative successful. Several studies have shown systemic, hypoglycemic effects after administration of a liposome containing insulin (e.g., Patel et al, FEBS Letters, 62, 60 (1976); Hashimoto et al, Endocrinol., Japan, 26, 337 (1979)). However, liposomes are still in the development stage of their use as oral hypoglycemic agents and face continued problems of stability, shelf-life, and so forth.
The difficulties of preparing other peptide and protein hormones (and other biologically active peptides and proteins) for oral ingestion or other types of enteral administration parallel the problems associated with insulin. Accordingly, there remains a need for a composition generally capable of effecting the oral administration of biologically active peptides and proteins.
Similarly it has long been established that heparin is an effective and safe blood anticoagulant. However, therapeutic use of heparin is limited by the need to administer it parenterally. A great deal of effort has been spent on the development of adjuvants, derivatives, analogs and expedients to render heparin absorbable from the intestine, so that it may be orally administered. This effort includes adjuvants such as heparin coadministered with ethylenediaminetetraacetate, EDTA (Windsor et al, "Gastrointestinal Absorption of Heparin and Synthetic Heparinoids", Nature, 190, 263-264 (1961); Tidball et al, "Enhancement of Jejunal Absorption of Heparinoid by Sodium Ethylenediaminetetraacetate in the Dog", Proc. Soc. Exp. Biol. Med., 111, 713-715 (1962); Rebar et al, "Forderung der Gastrointestinalen Resorption von Heparin durch Calciumbindungsmittel", Experientia, 19, 141-142 (1963)), with dimethylsulfoxide, DMSO, and diethylsulfone, and their homologs (Koh, T. Y., "Intestinal Absorption of Heparin", Can. J. Biochem., 47, 951-954 (1969)); derivatives such as heparin that underwent partial desulfation and methylation (Salafsky et al, "Intestinal Absorption of a Modified Heparin", Proc. Soc. Exp. Biol. Med., 104, 62-65 (1960)) or heparinic acid and/or heparinic acid complexes (Koh et al, "Intestinal Absorption of Stable Heparin Acid Complexes," J. Lab. Clin. Med., 80(1), 47-55 (1972)); analogs (Jarrett et al, "Effect of Intravenous and Oral Administration of Heparinoids G 31150, G-31150-A, and of Nitrolotriacetic Acid on Blood Coagulation", Throm. Diath Haemorrh, 25, 187-200(1971)); and expedients, such as instillation of heparin in acidic solutions in the animal intestinal loop (Loomis, T. A., "Absorption of Heparin from the Intestine", Proc. Soc. Exp. Biol. Med., 101, 447-449 (1959); Sue, T. K., "Heparin, Physical and Biological Factors in Absorption" in "Heparin: Structure, Cellular Functions and Clinical Applications", Ed., N. M. McDuffie, Academic Press, New York, 1979, pp. 159-166). Windsor, U.S. Pat. No. 3,088,868, discloses orally administrable heparin comprising heparin complexed with the alkali metal salts of amino acids or polyaminepolyacids, e.g., salts of EDTA. Koh et al, U.S. Pat. Nos. 3,506,642 and 3,577,534, disclose heparin complexed with weakly basic compounds (pk.sub.B =7.0-12.5) being useful as an orally active medicament. However, too highly basic materials, e.g., aliphatic amines, are taught to produce materials which are not orally active. Engel et al, U.S. Pat. No. 3,574,832, disclose a heparin composition for oral, intraduodenal or rectal administration comprising heparin and a sulfate-type surfactant. Sache et al, U.S. Pat. No. 4,239,754, discloses orally active heparin compositions comprising heparin retained on or in liposomes, the lipids of said liposomes are preferably phospholipids comprising acyl chains derived from nonsaturated fatty acids.
While limited success has been achieved in the direction of increasing heparin absorbability from the intestine, these efforts have not yet reached the stage that heparin can be administered orally to give a sustaining systemic anticoagulant effect. In short, these efforts to develop an orally administered heparin for use in clinical anticoagulant therapy have so far been unsuccessful.
In related work, complexes of heparin with quaternary ammonium ions such as tridodecylmethyl ammonium chloride, TDMAC (Leininger et al, Science, 152, 1625(1966); Grode et al, J. Biomed. Mater. Res. Symp., 3,77 (1972)), benzalkonium chloride, BKC (Grode et al, J. Biomed. Mater. Res. Symp., 3,77 (1972); Gott, U.L., Adv. Exp. Med. Bio., 52 35 (1975)), and cetylpyridinium chloride, CPC (Schmer et al, Trans. Am. Soc. Artif. Intern. Organs, 22,654 (1976)), have been proven to render heparin soluble in organic solvents. The heparin-surfactant complexes have been successful in the coating of internal surfaces of plastic medical appliances. Chang, U.S. Pat. No. 3,522,346, discloses the preparation of non-thrombogenic microcapsules wherein the encapsulating membrane incorporates or has on its surface a quaternary ammonium-heparin complex. Suitable quaternary ammonium compounds are benzalkonium, cetyltrimethylammonium and cetyldimethylbenzyl-ammonium. Harumiya et al, U.S. Pat. No. 3,844,989, discloses antithrombogenic polymer compositions, useful in the production of medical appliances, comprising a polymer containing cationic monomer units and heparin internally bound thereto. Grotta, U.S. Pat. No. 3,846,353, discloses a method of making a non-thrombogenic plastic material by exposing the plastic to a water-insoluble, organic solvent-soluble long chain alkyl quaternary ammonium salt having 2-4 alkyl groups and then exposing the plastic to heparin. Subsequent exposure of the plastic to blood plasma failed to release heparin in an anticoagulant effective amount. Ericksson et al, U.S. Pat. No. 4,265,927, disloses a method of heparinizing the surface of a medical article by contacting the article with a complex of heparin and a cationic surfactant, preferably of the primary amine type. Marchisio et al, U.S. Pat. No. 3,865,723, discloses the use of polymers with a polyamidic-aminic structure to remove heparin from blood.
Surfactants like BKC and CPC are cationic surfactants and widely used as antimicrobials (The Extra Pharmacocopia, Matindale, 27th Ed., The Pharmaceutical Press, London (1977)) and are quite toxic, e.g., LD.sub.50 of CPC, i.v. (mouse) is 10 mg/kg, i.v. (rat) is 6 mg/kg (Registry of Toxic Effects of Chemical Substances, U.S. Dept. HEW, 1975 Edition). Their toxicity is related to those various biological effects of quaternary ammonium heads whose effects include the depolarization of muscle tissue and hemolysis of erythrocytes. Toxic symptoms include dyspnoea and cyanosis due to paralysis of the respiratory muscles, possibly leading to asphyxia (Gastmeier et al, Z. Ges. Gerich. Med., 65, 96 (1969)) and allergic reactions, after repetitive applications of quaternary ammonium salt solutions to the skin, which have been reported to occur in some patients (Morgan, J. K., Br. J. Clin. Prac. 22, 261 (1969); Lansdown et al, Br. J. Derm., 86, 361(1972)). It is also believed that the surfactant characteristics of the quaternary ammonium ion, particularly in the liver, causes additional alterations in a number of chemical, biological and transport phenomena (Bohr et al, "Labile Quaternary Ammonium Salt as Soft Antimicrobials", J. Med Chem. 23, 469-474 (1980)).
A related problem in biochemistry is to be able to contact tumor cells spread along the hymphatic pathways which metastasize in the lymph nodes with intact antineoplastic drugs and agents. Presently, such agents have been subject to the same problems discussed in the above discussion. As such contact of antineoplastics with tumor cells in the lymph nodes has not been very successful.